1. Field of the Invention
The present invention relates generally to resistance welding and more specifically to a method for controlling and adaptively changing weld energy based on expulsion occurrence.
2. Description of Related Art
Resistance welding is used to weld pieces of metal together. Typically resistance welding uses two large electrodes that are placed on opposite sides of the surface to be welded. A large electric current passes through the electrodes and correspondingly heats up the metal between the electrodes. The result is a small area that is quickly heated to the melting point, forming a small spot of welded metal.
Achieving a good weld starts with a good process design that controls the welding variables such as weld energy and time. For example, if not enough weld energy is applied, a cold weld may result caused by insufficient heat at the welding interface whereby fusion occurs only between the point contacts of the two pieces of metal. Conversely, if too much weld energy is applied for too long, expulsion may occur. Expulsion is the forceful ejection of molten metal from the welds and often results in material burn through.
In the interest of obtaining good welds, it is desirable to monitor the welding process and adaptively change the weld energy as necessary to maintain weld quality.